The invention relates to gearing for motor driven timing relays of single and multiple range design. In motor driven timing relays of this type, a switching gear is driven by a synchronous motor via a gear box. The speed of an a.c. fed synchronous motor is stepped down by means of a multistage gear box so that the switching gear rotates by a given angle which is proportional to the set running time. This angle is as a rule smaller than 360.degree.. The gear box consists of a number of gear pairs which are in cascaded engagement with each other. The choice of the timing range is accomplished by inserting a predetermined number of gear pairs between the motor pinion and the switching gear. This choice can be accomplished in various ways. As a rule, the gear pairs, which are in continuous engagement with each other, are arranged in a stationary manner, the coupling between the gear pairs and the pinion of the coupling shaft being accomplished by one or several intermediate gears. In one known design, the individual gear pairs are arranged concentrically about the switching shaft and the individual timing ranges are taken off in 6 steps by a so-called traveling pinion which is rotatably supported on a rotatable disc. The range is set by means of a setting shaft which cooperates via a pinion with teeth on the rotatable disc. For exact adjustment the rotatable disc is further provided with detents which interact with a detent spring or the like.
In another known design, the gear pairs meshing with each other are arranged on two parallel shafts in cascade fashion, and a pinion whose shaft is fastened to the rotatable disc is associated with each gear pair. The pinions themselves are again connected to the drive motor via a traveling pinion.
In another design, the continuously meshing gear pairs are again arranged on two parallel shafts in cascade fashion and cooperate with pinions which are rotatably supported on a rotatable disc. Output pinions which are in driving connection with a pinion of the coupling shaft are fastened at the other end of the rotatable shafts.
In these designs of the gearing, the relatively high cost of the parts and the production quality required to ensure reliable functioning with a tolerance chain corresponding in length to the length of the chain of cooperating parts are all disadvantages.